Imaging display and storage methods effected with an integrated field emission array sensor, display, and transmitter

ABSTRACT

A method for displaying and storing or otherwise recording images includes use of an image detection apparatus that includes a field emission array with an image-sensing surface, an image-displaying surface opposite the image-sensing surface, and integral signal transmission circuits. As appropriate voltages are applied and the image-sensing surface of the field emission array is exposed to an image, p-n junctions near the image-sensing surface generate electron-hole pairs, which cause electrons to be transferred to a corresponding n-well. The change in voltage may result in the emission of electrons from an emitter tip that corresponds to the n-well and, thus, the display of an image by a display panel positioned adjacent to, but spaced apart from, the image-displaying surface. Additionally, changes in voltage in the n-well may be communicated in such a way that they are stored or recorded.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/386,906,filed Aug. 31, 1999, pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an integrated apparatus that senses ordetects electromagnetic radiation and displays the sensed or detectedradiation. Particularly, the present invention relates to an apparatusthat senses or detects electromagnetic radiation of visible or nearinfrared wavelengths and that displays the sensed or detected radiationin the form of a visible image. More particularly, the present inventionrelates to an apparatus that senses or detects electromagneticradiation, displays an image representative of the sensed or detectedradiation, and transmits signals representative of the detectedradiation. The present invention also relates to devices that includethe inventive apparatus.

2. Background of Related Art

Semiconductor devices, such as charge coupled devices (“CCDs”) have longbeen employed to detect radiation, such as electromagnetic radiation.Charge coupled devices typically include an array of pixels, each ofwhich includes an n-well, which is a region of n-type or n-dopedsilicon, in a p-type, or p-doped, silicon substrate. N-typesemiconductor regions are typically relatively negatively electricallycharged and conduct current by means of electrons. P-type semiconductorregions are relatively positively electrically charged and conductcurrent by means of electron hole pairs. The junction between the p-typesubstrate and the n-well, which is also referred to as a p-n junction oras a depletion region, typically has little or no mobile electricalcharge. As radiation (e.g., photons) impinges the p-n junction,electron-hole pairs proportionate to the amount of radiation are createdtherein. Stated another way, as the p-n junction of a pixel isirradiated, electrons, or electrical impulses, move from the p-njunction into the adjacent n-well of the pixel.

Since the p-n junctions of charge coupled devices convert radiation toan electrical signal, charge coupled devices have been employed todetect radiation (e.g., electromagnetic radiation), and to transmitelectrical signals representative of the detected radiation by means ofcircuitry associated with the pixels of these charge coupled devices.Accordingly, charge coupled devices have been used in various imagedetection applications, such as in digital cameras.

Some field emission arrays similarly include a p-type silicon substratewith relatively electrically conductive n-wells extending therethroughand, therefore, p-n junctions. Field emission arrays have conventionallybeen employed in association with cathodo-luminescent display panels, inthe form of field emission displays (“FEDs”), in order to displayimages.

Typically, the field emission array of a field emission display includesan array of emission pixels, each of which includes one or moresubstantially conical emitter tips. Each of the emitter tips iselectrically connected to a relatively negative voltage source, or anelectron source, by means of a cathode conductor line, which is alsotypically referred to as a column line.

Another set of electrically conductive lines, which are typicallyreferred to as row lines or as gate lines, extend over the emissionpixels of the field emission array. Row lines typically extend across afield emission display substantially perpendicularly to the direction inwhich the column lines extend. Accordingly, the paths of a row line andof a column line typically cross proximate (above and below,respectively) the location of one or more emitter tips. The row lines ofa field emission array are electrically connected to a relativelypositive voltage source. Thus, as a voltage is applied across both thecolumn line and the row line that intersect at one or more emissionpixels, electrons are emitted by the emitter tips of those emissionpixels and accelerated through an opening in the row line.

As electrons are emitted by emitter tips and accelerate past the rowline that extends over the emission pixel, the electrons are directedtoward a corresponding display pixel of a positively chargedcathodo-luminescent panel of the field emission display, which is spacedapart from and substantially parallel to the field emission array. Aselectrons impact a display pixel of the cathodo-luminescent panel, thedisplay pixel is illuminated. The degree to which the display pixel isilluminated depends upon the number of electrons that impact the displaypixel.

As the field emission array and its associated cathodo-luminescentdisplay are both generally planar structures and are disposed relativelyclose to one another, the field emission display (“FED”) devices ofwhich the field emission array and cathodo-luminescent display are apart are typically relatively thin, flat devices. Thus, field emissiondisplays are compact relative to display devices that include cathoderay tubes, and have found widespread use in many types of portableelectronic devices, such as portable computers and video cameras, or“camcorders”.

Field emission arrays have also been employed to detect radiation (e.g.,electromagnetic radiation of a visible wavelength or electrons) and totransmit electrons representative of the detected radiation. Exemplarydevices which employ field emission arrays in such a manner aredisclosed in U.S. Pat. No. 3,466,485 (hereinafter “the '485 Patent”),issued to John R. Arthur, Jr. et al. on Sep. 9, 1969; U.S. Pat. No.3,814,968 (hereinafter “the '968 Patent”), issued to Harvey C. Nathansonet al. on Jun. 4, 1974; U.S. Pat. No. 5,804,833 (hereinafter “the '833Patent”), issued to Roger Stettner et al. on Sep. 8, 1998; and U.S. Pat.No. 5,818,500 (hereinafter “the '500 Patent”), issued to Jon K. Edwardset al. on Oct. 6, 1998.

The '485 Patent discloses a light sensitive field emission array withemitter tips that intensify a detected light image. As light is directedtoward the back side of the field emission array, photons create currentin the emitter tips corresponding to the areas of the back side uponwhich light is directed.

The '968 Patent discloses a radiation sensitive field emission arraythat is similar to that disclosed in the '485 Patent. The emitter tipsof the field emission array of the '968 Patent emit electrons inresponse to an input radiation, such as light or electrons. The emittedelectrons are directed to a display screen that displays the detectedimage.

The field emission array of the '833 Patent detects and displays imagesin a similar manner. In addition to detecting and displaying visiblelight images, however, the field emission array of the '833 Patent canalso detect electromagnetic radiation wavelengths from visible light upto far infrared wavelengths (i.e., from about 300 nm up to about 1×10⁶nm) and display images representative of electromagnetic radiation ofthese wavelengths. Applicable uses of such a field emission array wouldbe in so-called “night vision” applications.

These patents do not, however, disclose field emission arrays thatinclude components that transmit signals representative of the detectedimages. Thus, the radiation-sensitive field emission arrays of thesepatents may not be employed to detect radiation, to display imagesrepresentative of the radiation, and to substantially simultaneouslytransmit signals representative of the radiation to another source, suchas to recording componentry.

Accordingly, there is a need for a field emission array that detectsradiation and substantially simultaneously displays an imagerepresentative of the detected radiation and transmits detectablesignals representative of the radiation. A relatively compact apparatusthat detects radiation and displays images and transmits signals thatare representative of the radiation is also needed.

SUMMARY OF THE INVENTION

The integrated field emission array sensor, display, and transmitter ofthe present invention includes a field emission array having asemiconductor substrate with an array of n-wells and, thus, p-njunctions defined therein, an array of emitter tips adjacent andcorresponding to the p-n junctions, and circuitry associated with eachpixel of the array.

The field emission array substrate is preferably a semiconductivematerial, such as silicon. The substrate may be p-type or p-dopedsemiconductor material, and therefore conducts current by means ofelectron hole pairs (i.e., the p-type semiconductor material isrelatively electron deficient).

Regions of conductively doped n-type semiconductive material, which arereferred to herein as n-type semiconductor wells or simply as n-wells,are defined in the substrate. These n-wells may comprise the columnlines of a field emission array. N-type semiconductive materials conductcurrent by means of the free electrons of a dopant material.

The interface between each n-well and the p-type semiconductor substrateof the field emission array defines a so-called “p-n junction” or “n-pjunction”. A depletion region, which includes relatively non-chargedmaterials, exists at the p-n junction. Thus, as is known in the art, acontact potential exists at the p-n junction.

The back side of the substrate (i.e., p-type semiconductor material) ofthe field emission array comprises a radiation detection surface, whichis also referred to herein as a detection surface, as a sensor surface,or as a radiation sensitive surface. As radiation such as photons (i.e.,quanta of electromagnetic radiation) enter a pixel through the radiationdetection surface, the radiation impedes a p-n junction of the fieldemission array, and electron hole pairs are created in the p-n junction.

As electron hole pairs are created in the p-n junction, a substantiallyproportionate number of electrons move into the n-well from the p-njunction. Thus, the voltage of the n-well decreases. The radiationdetection surface is preferably shielded from further radiation until asignal representative of the radiation incident with the pixel has beentransmitted.

Each pixel of the inventive apparatus includes a signal transmissioncircuit associated with the n-well of that pixel. The signaltransmission circuit includes a capacitor, a first side of whichcommunicates with the n-well and a second side of which is a source nodeof a first transistor or otherwise communicates with a source node ofthe first transistor. The drain node of the first transistorcommunicates with a baseline potential (V_(DD)). A second transistorshares a source node with the first transistor. The drain node of thesecond transistor communicates with a scan circuit of a type known inthe art, such as the circuits employed in digital cameras.

As the voltage of the n-well of an emission pixel decreases, the voltageof the n-well is communicated to the first side of the capacitor. As thesource node of the first transistor and, thus, the second side of thecapacitor, is preferably charged to the baseline potential, the voltageat the second side of the capacitor and, thus, the voltage of the sourcenode of the second transistor drops until it is substantially the sameas the voltage of the n-well. Upon turning the second transistor “on”(i.e., upon opening the gate of the second transistor), the voltage istransferred to the drain node of the second transistor. The voltage ofthe second transistor, which is now substantially representative of theamount and type of radiation that impinged the p-n junction of theemission pixel, may then be measured by the scan circuit thatcommunicates with the drain node of the second transistor. Upon turningthe gate of the second transistor “off”, the source node of the secondtransistor is electrically isolated from the voltage of the n-well. Avalue representative of the voltage measured by the scan circuit at thedrain node of the second transistor, which represents the radiationdetected by the emission pixel, may then be stored, as known in the art.

Each emission pixel of the field emission array further includes atleast one emitter tip that protrudes from an emission surface of thefield emission array located opposite the detection surface. Theemission pixels are preferably disposed substantially over and incommunication with the associated n-wells of the field emission array.

As the gate of the first transistor is opened, the source node of thefirst transistor and, thus, the second side of the capacitor, is chargedto the baseline potential (V_(DD)). As a relatively positive voltage isapplied to a conductive member of an extraction grid, or grid anode,overlying the emission pixel, due to the potential difference betweenthe grid anode and the emitter tip, electrons may be drawn from then-well, into the associated emitter tip, and emitted from the emittertip. As the electrons are emitted from the emitter tip and through theextraction grid, they are directed toward a corresponding display pixelof an cathodo-luminescent display and illuminate the same in a mannerthat represents the wavelength or intensity of radiation that impingedthe emission pixel that corresponds to the display pixel upon impingingthe display pixel. The n-well will then return substantially to thebaseline potential. Another image may be detected and a representativesignal transmitted by exposing the radiation detection surface toradiation, closing the gate of the first transistor, and repeating theprocess.

Other features and advantages of the present invention will becomeapparent to those of ordinary skill in the art through consideration ofthe ensuing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic representation of a field emission array accordingto the present invention;

FIG. 1A is a schematic representation of a field emission arrayaccording to the present invention, which includes a detectionenhancement material to facilitate the detection infrared and longerwavelengths of electromagnetic radiation;

FIG. 2 schematically illustrates a circuit including transistors thatmay be employed in the field emission array according to the presentinvention;

FIG. 2A schematically illustrates a variation of the circuit depicted inFIG. 2, which includes a switch between the n-well and the capacitor;

FIG. 3 is a flow chart that illustrates the method of the presentinvention;

FIG. 4 is a schematic representation of a system wherein a fieldemission array according to the present invention is employed to detectradiation, to display images representative of the detected radiation;and to transmit signals representative of a magnitude or amount and awavelength or type of the detected radiation; and

FIGS. 5A and 5B are front and rear schematic representations,respectively, of a video camera including a field emission arrayaccording to the present invention which depicts the use thereof todetect radiation, to display images representative of the detectedradiation, and to transmit and record signals representative of thedetected radiation.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an emission pixel 14 of a preferred embodiment of afield emission array 10 according to the present invention, whichincludes a p-type semiconductor substrate 12, such as p-type silicon,with an array of emission pixels 14 and a signal transmission circuit 26associated with each emission pixel 14.

Each emission pixel 14 includes a region of n-type semiconductormaterial, which is also referred to herein as an n-well 16, such asn-type silicon, proximate an active surface of substrate 12. Theinterface between each n-well 16 and the surrounding p-typesemiconductor material of substrate 12 defines a p-n junction 17.Preferably, the thickness D of, or shortest distance across, the p-typeregion of substrate 12 between each n-well 16 and the back side ofsubstrate 12 facilitates the creation of electron hole pairs asradiation, such as photons of electromagnetic radiation, impinge p-njunction 17.

The thickness D between the back side of substrate 12 and n-well 16preferably facilitates the generation of electron-hole pairs in p-njunction 17 by visible wavelengths of electromagnetic radiation (i.e.,visible light). Thickness D may facilitate the generation of electronhole pairs in p-n junction 17 by infrared or other wavelengths ofelectromagnetic radiation.

Field emission array 10 also includes at least one emitter tip 18associated with each n-well 16. Each emitter tip 18 is laterallysurrounded by and, preferably, at least partially spaced apart from alayer 20 of dielectric material. An extraction grid 22, which isfabricated from an electrically conductive material, is disposed overlayer 20 and, therefore, over a surface of field emission array 10.Apertures 24 formed through extraction grid 22 are located substantiallyabove each emitter tip 18.

With continued reference to FIG. 1, the signal transmission circuit 26associated with each emission pixel 14 includes a first transistor 28,or baseline potential transistor, which is illustrated in phantom sincetransistor 28 extends into or out of the plane of the page, and a secondtransistor 30, which is also referred to herein as a signal transmissiontransistor. First transistor 28 and second transistor 30 may share ann-well 32, which acts as the drain 34, or drain node, of both firsttransistor 28 and second transistor 30. First transistor 28 alsoincludes a gate 36 and a source 38, or source node, both of which areillustrated in phantom. Source 38 may communicate with a drain voltage,V_(DD). Second transistor 30 includes a gate 40 and a source 42, whichis also referred to herein as a source node. Source 42 communicates witha scan circuit 44 of a type known in the art.

Although second transistor 30 is illustrated as ametal-oxide-semiconductor field-effect transistor (“MOSFET”), which is atype of insulated-gate field-effect transistor (“IGFET”), other types oftransistors, such as a junction field-effect transistor (“JFET”) mayalso be employed as second transistor 30. Similarly, first transistor 28may comprise an IGFET, a JFET, or any other type of transistor.

A capacitor 46 disposed between n-well 16 and signal transmissioncircuit 26 facilitates the generation of a current through signaltransmission circuit 26. Capacitor 46 includes a first conductivestructure 48, which is a conductive contact disposed in contact with then-well 16 of emission pixel 14, a second conductive component 52, and adielectric component 50, such as a glass or an oxide, disposed betweenfirst conductive component 48 and second conductive component 52.

The various components of field emission array 10, including n-wells 16,emitter tips 18, capacitor 46, and signal transmission circuit 26, maybe fabricated by known semiconductor device fabrication techniques.

With reference to FIGS. 2 and 3, and with continued reference to FIG. 1,a preferred embodiment of the radiation detection, display, and signaltransmission process of the present invention is depicted. FIG. 2 is aschematic representation of the circuit defined by n-well 16, capacitor46, and signal transmission circuit 26. FIG. 3 is a flow chartillustrating an image sensing, display, and signal transmission processaccording to the present invention.

While the processes of the present invention are occurring, anappropriate voltage or voltages are applied, at reference 100 of FIG. 3,to all of the components of the circuit, including extraction grid 22,the ground reference of the circuit, the substrate bias of the circuit,the circuit voltage, and the cathodo-luminescent display panel 66 (seeFIG. 4), if any, is biased at a substantially constant, relativelypositive voltage.

The n-well 16 and drain 34 of an emission pixel 14 are each charged to abaseline potential. Accordingly, the back side 13 of substrate 12 atemission pixel 14 is shielded from radiation, such as by a shutter 54.Alternatively, with reference to FIG. 2A, field emission array 10 mayinclude a shutter 45. At reference 101 of FIG. 3, gate 36 of firsttransistor 28 is turned “on” while the back side 13 of substrate 12 atemission pixel 14 is shielded from radiation. Alternatively, withreference again to FIG. 2A, gate 36 of first transistor 28 may be turned“on” while shutter 45 of FIG. 2A is in the closed position. Shieldingback side 13 or closing shutter 45 permits n-well 16 to return to itsoriginal, or base, voltage, prior to detecting radiation R from aportion of an object O. This original voltage sets the voltagedifference between grid 22 and emitter tips 18 below the thresholdvoltage that causes emitter tips 18 to emit electrons. Therefore, asshutter 45 is closed, emitter tips 18 do not emit electrons. As gate 36of first transistor 28 is turned “on”, at reference 101 of FIG. 3, asubstantially constant drain source voltage, which comprises thebaseline potential (V_(DD)), is transferred from source 38 of firsttransistor 28 to drain 34. Gate 36 is then turned “off”, at reference102 of FIG. 3.

At reference 104 of FIG. 3, the back side of substrate 12 is exposed toradiation, which impinges p-n junction 17, creating electron-hole pairsrepresentative of the intensity or type of radiation therein and causingelectrons to be transferred to n-well 16. Thus, as radiation impingesp-n junction 17, the voltage of n-well 16 drops, or decreases, to createa voltage difference between grid 22 and emitter tips 18, therebyfacilitating the emission of electrons from emitter tips 18. Changes inthe voltage of n-well 16 are communicated to first conductive component48 of capacitor 46, at reference 104 of FIG. 3. Thus, the voltage ofn-well 16 and any changes in the voltage thereof may be communicated toa first side of capacitor 46.

As the voltage on the n-well 16 side of capacitor 46, at firstconductive component 48, drops, the voltage on the drain 34 side ofcapacitor 46, at second conductive component 52, substantiallycorrespondingly drops. Capacitor 46 stores the voltage of drain 34 untilgate 40 of second transistor 30 is turned “on”, at reference 106 of FIG.3. As gate 40 of second transistor 30 is turned “on”, the reducedvoltage of drain 34 is communicated or transferred to source 42 oftransistor 30, which may be scanned, at reference 108 of FIG. 3, todetermine the intensity or type of radiation incident with emissionpixel 14.

At reference 110 of FIG.3, gate 40 may be turned “off” while the backside 13 of substrate 12 at emission pixel 14 remains shielded fromradiation. Gate 36 of first transistor 28 is turned “on” to charge drain34 back to V_(DD), which permits n-well 16 to return substantially toits original, baseline potential.

The process may then be repeated to detect, display, and transmit asignal representative of subsequent radiation “images”. Gate 36 of firsttransistor 28 may be turned “off” and radiation permitted to impinge theback side 13 of substrate 12 at emission pixel 14, at reference 102 ofFIG. 3, to facilitate the sensing or detecting of another image ofradiation by emission pixel 14 and the transmission of a signalrepresentative of the radiation through second transistor 30.

As the apparatus of present invention comprises a field emission arrayhaving an array of n-wells, each of the n-wells preferably has a signaltransmission circuit associated therewith. Accordingly, radiation may bedetected by each n-well of the apparatus, or by each emission pixelthereof, and signals representative of the radiation detected at each ofthe pixels may be transmitted to a scan circuit, or image processingcircuit, of a type known in the art, associated with each of the signaltransmission circuits. The scanned and processed data may then berecorded by known processes.

With reference to FIG. 4, a system 60 is shown, which includes fieldemission array 10, a scan circuit 62 associated with field emissionarray 10, a processor 63 in communication with scan circuit 62, arecording mechanism 64 in communication with processor 63, asubstantially flat display panel 66, or cathodo-luminescent display,spaced apart from field emission array 10 in substantially mutuallyparallel relation therewith, and other components, as known in the art.

Scan circuit 62 is preferably an image signal detector of a type knownin the art, which detects or measures the charge or potential at source42 (see FIGS. 1 and 2) of the second transistor 30 of each of theemission pixels 14 of field emission array 10. Processor 63, which ispreferably of a type known in the art, communicates with scan circuit 62to convert the voltage measured at each emission pixel 14 to datarepresentative of the wavelength or the intensity of the radiationimpinging emission pixel 14. Recording mechanism 64, which is alsopreferably of a type known in the art, communicates with processor 63and records or stores the data representative of the wavelength orintensity of radiation impinging emission pixel 14 along with thelocation of the emission pixel 14 from which the data was obtained.

Display panel 66 includes an array of display pixels 68, each of whichare positioned to correspond to an emission pixel 14 of field emissionarray 10. In use, cathodo-luminescent display panel 66 is charged to arelatively positive attraction potential, which is greater than therelatively positive potential of extraction grid 22 so as to attractelectrons emitted from the emitter tips 18 of field emission array 10,and which generates image light as electrons are attracted thereto.

FIG. 4 depicts the detection of electromagnetic radiation of orreflected by an object O and the display of an image I of object O bysystem 60. Preferably, electromagnetic radiation from object O isfocused on back side 13 of substrate by one or more optical lenses (see,e.g., optical lens 72 in FIGS. 1 and 5B). As back side 13 (see FIG. 1)of substrate 12 is exposed to electromagnetic radiation from object O,emission pixels 14 are exposed to different wavelengths and intensitiesof electromagnetic radiation from the different portions of object O towhich each emission pixel 14 is exposed.

The wavelength and intensity of the radiation from each portion ofobject O impinging a corresponding emission pixel 14 of field emissionarray 10 is translated to a corresponding electrical impulse in themanner described in reference to FIGS. 2 and 3. These electricalimpulses are measured by a scan circuit 62 of a type known in the art.Processor 63 processes the measurements taken by scan circuit 62, whichmay be recorded for each of the emission pixels 14 of field emissionarray 10 by recording mechanism 64, as known in the art. Thus, recordingmechanism 64 stores an array of information representative of theradiation from object O to which back side 13 of substrate 12 of fieldemission array 10 is exposed.

The emitter tip or tips 18 of each emission pixel 14 emit electrons in amanner that represents the wavelength and the intensity of the portionof radiation from object O to which emission pixel 14 is exposed. Theseelectrons are emitted upon application of a relatively positivepotential to extraction grid 22, as described above in reference toFIGS. 2 and 3. Thus, electrons representative of object O are emittedfrom the emission pixels 14 of field emission array 10 as emissionpixels 14 are exposed to radiation from object O. These emittedelectrons impinge display pixels 68 of display 66, eliminating displaypixels 68 that correspond to emission pixels 14 that have been exposedto a portion of the radiation from object O. Thus, display 66 displaysan image I representative of object O.

As an alternative to or in combination with recording mechanism 64,system 60 may include an image transmission mechanism of a type known inthe art, which transmits signals representative of radiation from objectO to a storage device, an output device, a processor, or another devicewhich may store, process, interpret, or otherwise utilize the signals ofscan circuit 62.

Although system 60 is depicted in FIG. 4 as including a display 66associated with field emission array 10, system 60 need not include sucha display. If system 60 does not include display 66, image I may bedisplayed by other components associated with scan circuit 64.

System 60 may be employed to detect a series of images and measure thewavelengths and intensities of portions of each image of the series ofimages incident with each emission pixel 14 of field emission array 10.These measured wavelengths and intensities at each emission pixel 14 maybe stored for each image of the series of images. Since scan circuit 62identifies the emission pixel 14 that detects the radiation of a portionof an image, information representative of radiation impinging eachemission pixel 14 of field emission array 10 is stored. Since thisinformation may be stored on an image-by-image basis, a videorepresentative of a series of images may be stored and played back.Thus, as shown in FIGS. 5A and 5B, the system 60 (see FIG. 4) of thepresent invention may be employed in a video camera 70. Of course, videocamera 70 also includes one or more optical lenses 72 that focuselectromagnetic radiation from an object O onto back side 13 ofsubstrate 12 of field emission array 10 (see FIG. 1) and othercomponents, as known in the art.

If field emission array 10 is capable of detecting infrared wavelengthsof electromagnetic radiation, system 60 or an image detection systemsimilar thereto may also be used in apparatus for detecting ordisplaying infrared images. For example, system 60 could be used innight-vision goggles.

A silicon substrate by itself has too high a band gap to detect longerwavelengths (e.g. 2,500 to 10,000 nm) of electromagnetic radiation.Accordingly, referring again to FIG. 1, field emission array 10 mayoptionally include a substrate 12 of low band gap material, which isalso referred to herein as a “detection enhancement material,” of a typeknown in the art to enhance detection of longer wavelengths ofelectromagnetic radiation by field emission array 10. Low band gapmaterials, such as mercury-cadmium-tellurium alloys and other materialshaving electrical characteristics that are more readily altered thanthose of silicon by electromagnetic radiation of relatively longwavelengths, may be used as substrate 12 to facilitate the detection ordisplay infrared radiation in thermal imaging applications or longerwavelengths of electromagnetic radiation. Detection enhancementmaterials such as mercury-cadmium-tellurium facilitate the detection byfield emission array 10 of wavelengths of electromagnetic radiation offrom about 1,000 nm to about 10,000 nm and greater.

Alternatively, with reference to FIG. 1A, a field emission array 10′configured to detect wavelengths of electromagnetic radiation that arelonger than visible light can include a silicon substrate 12′ with ap-type region 76 (e.g., p-type silicon) having a p-type conductivity andan n-type region 78 (e.g., n-doped silicon) having an n-typeconductivity. A diffusion region 77, or p-n junction, is located betweenp-type region 76 and back side 13′ of substrate 12′ and is proximate toback side 13′. A coating 74, or layer, of detection enhancement materialdisposed on back side 13′ proximate to diffusion region 77 facilitatesthe detection of radiation, the scanning of electrical impulsesrepresentative of the detected radiation, and the emission of electronsrepresentative of the detected radiation in a manner similar to thedetection, scanning, and emission effected by p-n junction 17 ofsemiconductor substrate 12. Alternative embodiments of field emissionarray 10′, as well as examples of useful low band gap materials anddopant concentrations, are disclosed in U.S. Pat. No. 6,441,542, issuedto Hush et al. on Aug. 27, 2002, the disclosure of which is herebyincorporated in its entirety by this reference.

Although the foregoing description contains many specifics and examples,these should not be construed as a limiting the scope of the presentinvention, but merely as providing illustrations of some of thepresently preferred embodiments. Similarly, other embodiments of theinvention may be devised which do not depart from the spirit or scope ofthe present invention. The scope of this invention is, therefore,indicated and limited only by the appended claims and their legalequivalents, rather than by the foregoing description. All additions,deletions and modifications to the invention as disclosed herein andwhich fall within the meaning of the claims are to be embraced withintheir scope.

1. A method for detecting electromagnetic radiation and storing datarepresentative of the electromagnetic radiation, comprising: exposing aback side of a field emission array to the electromagnetic radiation topermit the electromagnetic radiation to impinge a p-n junction adjacentto a corresponding n-well of the field emission array, resulting in thegeneration of electron-hole pairs in the p-n junction and thecommunication of a number of electrons representative of a wavelength oran intensity of the electromagnetic radiation to the at least onen-well, the increase in electrons in the n-well resulting in emission ofelectrons from at least one emitter tip of the field emission array thatis in communication with the at least one n-well; and communicating anelectrical charge created by the increase in electrons in the n-well toan adjacent side of a capacitor that is in communication with the n-wellto facilitate storage of a portion of an image; and
 2. The method ofclaim 1, further comprising: measuring a potential across the capacitor.3. The method of claim 2, wherein measuring comprises: communicating avoltage present at the adjacent side of the capacitor to an opposite,drain side of the capacitor; storing the voltage in the capacitor;turning a gate of a transistor that communicates with the drain side ofthe capacitor on to communicate the voltage across capacitor to a sourceof the transistor; and scanning the voltage of the source to determineat least one of an intensity and a wavelength of radiation that impingedthe p-n junction.
 4. The method of claim 3, wherein communicating thevoltage facilitates the emission of electrons from the at least oneemitter tip.
 5. The method of claim 4, further comprising: applying arelatively positive voltage to an extraction grid associated with the atleast one emitter tip to facilitate the emission of electrons from theat least one emitter tip.
 6. The method of claim 5, further comprising:applying a positive voltage to a display panel to facilitate the missionof electrons from the at least one emitter tip and illumination of atleast one corresponding pixel of the display panel as electrons impactthe at least one corresponding pixel.
 7. The method of claim 1, furthercomprising: storing a value representative of the potential across thecapacitor.
 8. The method of claim 1, further comprising: shielding theback side from the electromagnetic radiation.
 9. The method of claim 1,further comprising: re-exposing the back side to electromagneticradiation.
 10. The method of claim 1, wherein exposing comprisesfocusing an image comprising of the electromagnetic radiation onto theback side.
 11. The method of claim 1, wherein exposing comprisesdirecting the back side toward a source of electromagnetic radiation.12. The method of claim 1, wherein exposing comprises opening a shutter.13. A method for detecting, displaying, and recording an image,comprising: generating a change in voltage in n-wells associated with animage-sensing surface of a field emission array by orienting theimage-sensing surface toward the image; communicating the change involtage to capacitors that communicate with the n-wells to facilitatestorage or recording of the image; and communicating the change involtage to emitter tips that communicate with the n-wells to facilitatedisplay of the image by an image-display surface of the field emissionarray.
 14. The method of claim 13, further comprising: measuring apotential across each capacitor.
 15. The method of claim 14, whereinmeasuring comprises: communicating a voltage present at the adjacentside of each capacitor to an opposite, drain side of the capacitor;storing the voltage in the capacitor; turning a gate of a transistorthat communicates with the drain side of the capacitor on to communicatethe voltage across capacitor to a source of the transistor; and scanningthe voltage of the source to determine at least one of an intensity anda wavelength of radiation that impinged a p-n junction in communicationwith an n-well associated with the capacitor.
 16. The method of claim15, wherein communicating the voltage facilitates emission of electronsfrom an emitter tip in communication with the n-well.
 17. The method ofclaim 16, further comprising: applying a relatively positive voltage toan extraction grid associated with the field emission array tofacilitate the emission of electrons from the emitter tip.
 18. Themethod of claim 17, further comprising: applying a positive voltage to adisplay panel to facilitate the emission of electrons from the emittertip and illumination of at least one corresponding pixel of the displaypanel as electrons impact the at least one corresponding pixel.
 19. Themethod of claim 13, further comprising: storing values representative ofthe potentials across the capacitors.